Triple papermaking fabric

ABSTRACT

A papermaking fabric has a fabric repeating unit that comprises eight top MD yarns and eight bottom MD yarns that extend in machine direction; three top CMD yarns interwoven only with the top MD yarns; three bottom CMD yarns interwoven only with the bottom MD yarns; and two pairs of binding yarns interwoven with both the top MD yarns and the bottom MD yarns; the binding yarns of each pair cross each other under respective transition yarns; the binding yarns of each pair, together, leave exposed on a top surface of the fabric only single isolated transition yarns, all separated from each other in cross machine direction by a plurality of adjacent top MD yarns.

TECHNICAL FIELD

The present invention relates to a papermaking fabric, in particularintended for use as a forming fabric in a forming section of apapermaking machine.

BACKGROUND ART

The traditional fourdrinier papermaking process mainly provides threesuccessive steps, carried out in the corresponding sections of thepapermaking machine: forming section, pressing section, drying section.

In the forming section, an aqueous pulp of cellulose fibers (and anypossible other components) is arranged on a so-called forming fabric orcanvas, which is tape-shaped closed in a loop and supported by rollers.The removal of water from the pulp through the forming fabric leads tothe progressive formation of a wet paper material tape, with arelatively high water content still remaining. A further removal ofwater takes place in the pressing section, in which the paper materialis pressed by passing through one or more pairs of rollers. The papermaterial is then sent to the drying section for final moisture removal.The paper thus formed is ready for the subsequent finishing andpackaging steps.

In the following, as customary in the field of papermaking and relatedfabrics, the terms “machine direction” (abbreviated “MD”) and “crossmachine direction” (abbreviated “CMD”) are used to indicate respectivelya direction aligned with the feed direction of the forming fabric in thepapermaking machine, and a direction parallel to the fabric surface andcrosswise (perpendicular) to the feed direction. Also direction ororientation of the warp and weft yarns of the forming fabric areindicated with reference to the machine direction and cross machinedirection.

It is also intended, again as customary in the industry, that thesurface of the forming fabric in contact with the cellulose pulp (i.e.with the paper material being formed) is the top surface of the fabric;and that the opposite surface facing the machine is the bottom surface.This reference is also adopted to describe the vertical spatialarrangement of the yarns in the forming fabric.

Some characteristics of the papermaking fabrics are of particularimportance, such as the support capacity and filtration capacity,especially in the forming section.

Furthermore, the papermaking fabrics should show excellent stabilityeven when moved at high speeds, a high permeability to reduce the amountof water retained in the pulp when transferred to the pressing section,and a reduced energy consumption for the handling thereof.

Although various types of papermaking fabrics are known, in particularfor use in the forming section, margins of improvement in this fieldstill seem to be possible, for example in terms of mechanical strength,stability, life span, draining capacity and quality of the formed paper.

For example, WO2014/091410 describes a papermaking fabric having a toplayer formed by top CMD yarns interwoven only with top MD yarns; abottom layer formed by bottom yarns CMD interwoven only with bottom MDyarns; binding yarns are interwoven with both the top and bottom MDyarns, therefore binding the top and bottom layer.

On the other hand, it is known that even small changes of the structurecan unpredictably affect the fabric performance and therefore, theproperties of the paper manufactured from said fabric. It is well knownin the field that apparently even very similar structures can behave ina completely different manner.

In fact, the fabric structure has a direct impact on the quality of thepaper sheet being formed on the fabric, intimately in contact with thesame: but the way in which structural changes to the fabric may affectthe quality of the paper is not predictable.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide apapermaking fabric that maintains these characteristics to asatisfactory extent, resulting in particular, fully effective, highdrainage, resistant and stable in time, and ensuring the formation ofhigh quality paper.

The present invention therefore relates to a papermaking fabric asdefined, in essential terms, in the appended claim 1 and, in itsadditional characters, in the dependent claims.

The present invention also relates to the use of said fabric in apapermaking machine, and specifically in the forming section of themachine, as defined in the appended claim 18.

The invention provides a papermaking fabric which, as some knownfabrics, has a two layer structure, each of which is formed byindependent weft and warp yarns, and a binding system formed by pairs ofbinding yarns; however, the invention is distinguished by the specificfabric structure which allows a fully effective fabric to be obtained,high drainage, resistant and stable in time, and capable of ensuring theformation of high quality paper.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described in the following non-limitingexamples of embodiments, with reference to the accompanying figureswherein:

FIG. 1 is a schematic top plan view of a top fabric layer according tothe invention, of which a fabric repeating unit is shown;

FIG. 2 is a schematic top plan view of a bottom fabric layer of FIG. 1;

FIGS. 3a, 3b, 3c are sectional views according to the trace planesIIIa-IIIa, IIIb-IIIb, IIIc-IIIc of FIGS. 1 and 2, respectively;

FIG. 4 is a schematic top plan view of an alternative of the top fabriclayer according to the invention;

FIG. 5 is a schematic top plan view of a bottom fabric layer of FIG. 4;

FIGS. 6a, 6b, 6c, 6d are sectional views according to the trace planesVIa-VIa, VIb-VIb, VIc-VIc, VId-VId of FIGS. 4 and 5, respectively;

FIG. 7 is a view in machine direction (warp) of a detail of the fabricof the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIGS. 1-3, the number 100 denotes as a whole apapermaking fabric, in particular a forming fabric for use in theforming section of a papermaking machine.

The fabric 100 is a triple 16 harness fabric and comprises a top layer101 and a bottom layer 102 formed, as usual, by respective repeat unitswhich together form one fabric repeating unit 104; in FIGS. 1 and 2 asingle fabric repeating unit 104 is shown; it is understood that incommercial and industrial applications the unit 104, as well as therepeat units of the individual layers 101, 102, may be repeated severaltimes, both in machine direction and in cross machine direction, to forma fabric 100 having suitable sizes for use on a papermaking machine.

In general, the fabric 100 is formed by longitudinal warp yarns thatextend in machine direction (MD) and cross weft yarns, substantiallyorthogonal to the preceding ones, which extend in cross machinedirection (CMD). In the following (and as usual in the field), thelongitudinal warp yarns that extend in machine direction will beindicated, for brevity, as “MD yarns”, and cross weft yarns which extendin cross machine direction as “CMD yarns”.

In this case, a repeat unit 104 of the fabric 100 comprises eight top MDyarns 1-8, three top CMD yarns P6,P10,P14, eight bottom MD yarns 9-16,three bottom CMD yarns MC5,MC9,MC13, and four binding yarnsL7,L8,L11,L12 comprising respective support portions 115 and respectivebinding portions 116.

The top layer 101 comprises the top MD yarns 1-8 and the top CMD yarnsP6,P10,P14, as well as the support portions 115 of the binding yarnsL7,L8,L11,L12.

The bottom layer 102 comprises the bottom MD yarns 9-16 and the bottomCMD yarns MC5,MC9,MC13, as well as the binding portions 116 of thebinding yarns L7,L8,L11,L12 which extend to bind the bottom MD yarns9-16.

The top CMD yarns P6,P10,P14 are interwoven only with the top MD yarns1-8, and the bottom CMD yarns MC5,MC9,MC13 are interwoven only with thebottom MD yarns 9-16. The binding yarns L7,L8,L11,L12 bind the top MDyarns 1-8 with the bottom MD yarns 9-16.

The top MD yarns 1-8 and the top CMD yarns P6,P10,P14 are interwoven sothat each top CMD yarn P6,P10,P14 passes over three adjacent top MDyarns and under a following top MD yarn, and so on. For example, asshown in FIG. 3a , the top CMD yarn P6 passes under the top MD yarn 1,over the top MD yarns 2,3,4, under the top MD yarn 5, over the top MDyarns 6,7,8 and so on.

The same pattern is followed by all the top CMD yarns P6,P10,P14, butthe top CMD yarns are offset in cross machine direction, by one or twotop MD yarns, specifically.

In particular, the top CMD yarn P10 is offset by a top MD yarn withrespect to the preceding top CMD yarn P6 (then passing under the top MDyarns 2, 6 and over the remaining top MD yarns 1,3,4,5,7,8), and the topCMD yarn P14 is offset by two top MD yarns with respect to the precedingtop CMD yarn P10 (then passing under top MD yarns 4,8 and over theremaining top MD yarns 1,2,3,5,6,7).

The layers 101, 102 are joined and bound together to form the fabric 100by means of the binding yarns L7,L8,L11,L12.

Each binding yarn L7,L8,L11,L12 comprises, in a fabric repeating unit104, a support portion 115, which is arranged over the top MD yarns 1-8and is interwoven with the same, and a binding portion 116, which isarranged under the top MD yarns 1-8 and is interwoven with the bottom MDyarns 9-16.

The binding yarns L7,L8,L11,L12 are arranged in pairs between pairs ofadjacent top CMD yarns P6,P10,P14. Each pair of binding yarns L7,L8 andL11,L12 is arranged between two adjacent top CMD yarns P6,P10,P14.

In particular, the pair of binding yarns L7,L8 is arranged between thetop CMD yarns P6,P10, and the pair of binding yarns L11,L12 is arrangedbetween the top CMD yarns P10,P14.

The binding yarns L7,L8; L11,L12 of each pair (though represented sideby side, for clarity, in relation to the out of scale schematic views ofFIGS. 2 and 3) are interwoven together and are vertically overlapped, sothat the support portions 115 of a binding yarn of the pair areoverlapping the binding portions 116 of the other binding yarn of thepair, and vice versa; the two binding yarns of a pair cross each otheralong some of the top MD yarns 1-8 which define respective transitionyarns T, which pass over both the binding yarns of the pair and underwhich, the binding yarns of the pair cross each other, which define thetransition between the support portions 115 and the binding portions116.

The binding yarns L7,L8; L11,L12 of each pair, together, leave exposed(on the top surface of the fabric 100) only single isolated transitionyarns T. For each pair of binding yarns L7,L8; L11,L12 each transitionyarn T is separated from the other transition yarns T in cross machinedirection by a plurality of other top MD yarns; in other words, thetransition yarns T are all separated from each other in cross machinedirection by a plurality of other top MD yarns. There are, therefore,only individual transition yarns T (not adjacent to one another),regularly spaced from one another in the cross machine direction by aplurality of other top MD yarns. There are, instead, no adjacenttransition yarns T. In particular, the transition yarns T are separatedfrom each other by other three adjacent top MD yarns.

For the pair of binding yarns L7,L8 the transition yarns T are the topMD yarns 4 and 8; for the pair of binding yarns L11,L12 the transitionyarns T are the top MD yarns 3 and 7. The transition yarns T of eachpair of binding yarns L7,L8; L11,L12 are spaced by three adjacent top MDyarns; the transition yarns T of the two pairs of binding yarns L7,L8;L11,L12 are offset by one top MD yarn.

Each of the binding yarns L7,L8,L11,L12 passes over three adjacent topMD yarns 1-8 (defining a supporting portion 115) and under the followingfive adjacent top MD yarns 1-8 (defining a binding portion 116).

The binding yarns L7,L8; L11,L12 of each pair are interwoven so that thesupport portions 115 of one are arranged over the binding portions 116of the other.

The two binding yarns L7,L8; L11,L12 of each pair, together, pass overthree adjacent top MD yarns, under a following top MD yarn and so on,following the same pattern (i.e. the same interlacing) of the top CMDyarns P6,P10,P14. The pairs of binding yarns L7,L8; L11,L12, however,are offset with respect to adjacent top CMD yarns (between which thepair of binding yarns is arranged), so as to pass over the top MD yarnsthat are left exposed by the adjacent top CMD yarns.

Both binding yarns L7,L8,L11,L12 of a pair pass under the transitionyarns T.

For example (FIG. 3b ), the binding yarn L7 passes over the top MD yarns1,2,3 with its own support portion 115 and passes under the top MD yarns4,5,6,7,8 with its own binding portion 116; the binding yarn L8 (FIG. 3c) passes over the top MD yarns 5,6,7 with its own support portion 115,as it passes under the top MD yarns 1,2,3,4,8 with its own bindingportion 116. Both binding yarns L7, L8 pass under the transition yarns Tdefined by the top MD yarns 4 and 8.

In the fabric repeating unit 104, each binding yarn L7,L8,L11,L12 binds(passes over) a tern of adjacent top MD 1-8 yarns and binds (passesunder) a bottom MD yarn 9-16, in particular being offset in the machinecross direction by an even number of positions (for example, twopositions or four positions) with respect to the tern of top bound MDyarns.

For example, the binding yarn L7 (FIG. 3b ) passes over (i.e. binds) thetop MD yarns and under 1,2,3 (i.e. binds) the bottom MD yarn 15, whichis offset by four positions in cross machine direction with respect tothe top MD yarn 3; the binding yarn L8 (FIG. 3c ) passes over the top MDyarns 5,6,7 and under the bottom MD yarn 9, which is offset by twopositions in cross machine direction with respect to the top MD yarn 7.

In the other pair of binding yarns L11,L12, the binding yarn L11 passesover (i.e. binds) the top MD yarns 1,2,8, and under the top MD yarns3,4,5,6,7 and passes under (i.e. binds) the bottom MD yarn 14, which isoffset by four positions in cross machine direction with respect to thetop MD yarn 2; the binding yarn L12 passes over the top MD yarns 4,5,6,under the top MD yarns 1,2,3,7,8 and under the bottom MD yarn 10, whichis also offset by four positions in cross machine direction with respectto the top MD yarn 7.

Ultimately, each binding yarn L7,L8,L11,L12 passes over three adjacenttop MD yarns 1-8 and under the following five adjacent top MD yarns 1-8,and so on; and under one bottom MD yarn 9-16 and over all the followingbottom MD yarns 9-16, and so on.

In this way, the binding yarns L7,L8,L11 L12 and the top CMD yarnsP6,P10,P14 form a four satin structure (four harness satin) with the topMD yarns 1-8 (FIG. 1).

The bottom layer 102 (FIG. 2) comprises the bottom MD yarns 9-16, thebottom CMD yarns MC5,MC9,MC13 and the binding portions 116 of thebinding yarns L7,L8,L11,L12.

The bottom CMD yarns MC5,MC9,MC13 are interwoven with the bottom MDyarns 9-16 with a “over-2/under-6” sequence. For example, as shown inFIG. 3a , the bottom CMD yarn MC5 passes over the bottom MD yarns 10,11and under the bottom MD yarns 9 and 12-16.

The other bottom CMD yarns MC9,MC13 follow a similar pattern“over-2/under-6” with respect to the bottom MD yarns 9-16, but each isoffset with respect to the adjacent bottom CMD yarn in cross machinedirection (in particular by one position) so as to form an interruptedsix harness twill structure.

The bottom layer 102 comprises, furthermore, the binding portions 116 ofthe binding yarns L7,L8,L11,L12.

As already described, each binding yarn L7,L8,L11,L12 binds, in thefabric repeating unit 104, three adjacent top MD yarns 1-8 and onebottom MD yarn 9-16; in particular, each binding yarn L7,L8,L11,L12binds (by passing over) a tern of adjacent MD yarns 1-8 and (by passingover) one bottom MD yarn 9-16 which is offset by two or four positionsin cross machine direction with respect to the tern of top MD yarns(specifically, with respect to the third and last top MD yarn of thetern).

For example, the binding yarn L7 (FIG. 3b ) passes over (i.e. binds) thetop MD yarns 1,2,3 and passes under (i.e. binds) the bottom MD yarn 15,which is offset by four positions in cross machine direction withrespect to the top MD yarn 3; the binding yarn L8 (FIG. 3c ) passes overthe top MD yarns 5,6,7 and under the bottom MD yarn 9, which is offsetby two positions in cross machine direction with respect to the top MDyarn 7.

Each binding yarn L7, L8, L11, L12 passes over a tern of adjacent top MDyarns and under the following five top MD yarns, and so on; and underone bottom MD yarn, and over the following seven bottom MD yarns, and soon.

The binding yarns L7,L8; L11,L12 of each pair, together, with respect tothe top MD yarns 1-8, follow a sequence identical to the sequence of thetop CMD yarns P6,P10,P14 with respect to the top MD yarns 1-8. Inparticular, the binding yarns L7,L8,L11,L12 of each pair follow an“over-3/under-1” sequence with respect to the top MD yarns 1-8, whichis, specifically, the same sequence of the top CMD yarns P6,P10,P14 withrespect to the top MD yarns 1-8.

Again, the binding yarns L7,L8; L11,L12 of each pair, together, followan “under-1/over-5” sequence (pair of binding yarns L7,L8), or an“under-1/over-3” sequence (pair of binding yarns L11,L12), with respectto the bottom MD yarns 9-16.

Alternatively, the two pairs of binding yarns L7,L8; L11,L12 can followthe same sequence (and in particular one of the two indicated),preferably being offset by one position in cross machine direction withrespect to one another.

The interweave of the yarns L7,L8,L11,L12 with the top MD yarns 1-8 andbottom MD yarns 9-16 can however assume other shapes.

As can be seen, as a whole, from the figures in the repeat unit 104 ofthe fabric 100 there are eight bottom MD yarns and eight top MD yarns.

The fabric 100 has a ratio between weft and warp yarns of 4:1.

It is intended as ratio between the weft and warp yarns the ratiobetween the number of weft yarns that are repeated to form the fabric inmachine direction and the number of the warp yarns that are repeated incross machine direction to form the fabric.

In the fabric 100 there are four weft yarns for each warp; thiscorresponds to the manufacturing mode of the fabric: in the weaving on aloom, four weft yarns are inserted for each warp yarn.

In cross section (section perpendicular to the machine direction), thefabric 100 thus has a sequence of four weft yarns that are repeated inmachine direction for each warp yarn (that is alternately a top orbottom yarn depending on the weaving with the weft yarns).

In other words, the fabric repeating unit 104 is formed by a single warpyarn (MD yarn) every four weft yarns (CMD yarn): for each warp yarn(which can be a top MD yarn 1-8 or a bottom MD yarn 9-16, depending onthe weave with the weft CMD yarns), there is in fact one top CMD yarn(one of P6,P10,P14), one bottom CMD yarn (one of MC5,MC9,MC13) and apair of binding yarns (L7,L8; L11,L12).

In FIGS. 3a, 3b, 3c of the warp yarns are schematically shown overlappedin pairs to form the two layers; in reality, the warp yarns are thusarranged due to the interweaving effect with the weft yarns, but incross machine direction there is only one warp yarn which is repeated.

The ratio between weft and warp yarns of 4:1 reflects the weaving modeof the fabric 100; at each beat (or insertion) of the fabric formingframe, on each warp yarn four consecutive weft yarns are inserted.

The fabric 100 has, therefore, a warp yarn every four weft insertions.Each top or bottom MD yarn is associated, in every frame insertion orbeat, with a top CMD yarn, a bottom CMD yarn and a pair of bindingyarns.

Those skilled in the art will recognize that the fabrics, according tothe present invention, can take various shapes.

For example, with respect to what has been previously described, thenumber and/or the position of the binding yarn with respect to thenumber and/or the position of the top CMD yarns can be varied (forexample there can be a binding yarn every two or three top CMD yarns, orthere can be two or three or more binding yarns for each top CMD yarn).

Also the number of the top and bottom CMD yarns of the fabric repeatingunit can vary with respect to what is described and illustrated purelyby way of example.

Moreover, all the weaving patterns or structures described for thelayers 101, 102 can be different from those illustrated and described;for example, the top surface of the fabric does not necessarily need tobe formed by a four harness satin structure as shown, but can be likecanvas, twill, broken twill, etc.; and the bottom surface of the fabricdoesn't need to be a six harness broken twill structure, but can haveanother shape, such as a broken satin, plain structure (canvas), abroken twill, a twill, etcetera. Again, further alternative structurepatterns may be used in the fabric according to the present invention.

Yarns of various shapes (for example having a rounded or flattenedsection) and size.

The shape of the yarns used in the fabric of the invention can vary,also depending on the properties to impart to the final product. Forexample, the yarns may be monofilament yarns, flat monofilament yarns,multifilament yarns, multifilament or monofilament interwoven yarns,yarns of any kind, or any combination thereof. The materials of whichthe yarns are made of, can be those commonly used in the field. Forexample polyester, polyamide, polyamide/polyester yarns, or the like canbe used. The technician skilled in the art will be able to select thematerials of the yarns also as a function of the specific applicationfor which the final fabric is intended to be used.

For example, the top MD yarns, the top CMD yarns and the binding yarnscan have a diameter (equal or different from one another) comprisedbetween about 0.10 and 0.25 mm; the bottom MD yarns can have a diameterbetween about 0.12 and 0.30 mm; the bottom CMD yarns can have a diameterbetween about 0.10 and 0.35 mm; these are purely exemplary dimensions,and yarns of other sizes can be used depending on specific needs. Theknit also (i.e. the knit size) of the fabric may also vary. For example,the knit size of the top surface can be between about 34×38 and 37×48(warp yarns per cm×weft insertions per cm) and the total knit size mayvary between about 66×74 and 78×96 (warp yarns per cm×weft insertion percm).

A fabric with a ratio of 4:1 and with the bottom layer having an sixharness interrupted twill structure, produced according to theinvention, has, for example, the characteristics shown in Table 1.

TABLE 1 YARN Dimensions top MD 0.12 mm bottom MD 0.12 mm binding 0.11 mmtop CMD 0.11 mm bottom CMD 0.18 mm mesh (top surface) 37 × 44 * mesh(total) 74 × 88 * * warp yarns per cm × weft insertions per cm

In FIGS. 4-6, wherein the details similar or identical to those alreadydescribed are indicated with the same reference numbers, an alternativeof the fabric 100 of the invention is shown.

As shown in FIGS. 4 and 6 a, the top layer 101 still has a four satinstructure: the top CMD yarns, of which only a pair of adjacent yarnsP14,P2 are represented, are in fact interwoven with the top MD yarns 1-8with a sequence “over-3/under-1” (each top CMD yarn passes over threeadjacent top MD yarns and under a following top MD yarn, and so on).

As shown in FIGS. 5 and 6 b, the bottom layer 102 has a structure: thebottom CMD yarns, of which only a pair of adjacent yarns MC13,MC1 arerepresented, are interwoven with the bottom MD yarns 9-16 with asequence “over-3/under-1” (each bottom CMD yarn passes over one bottomMD yarn and under the following three adjacent bottom MD yarns, and soon).

FIGS. 4, 5, 6 c and 6 d show a pair of binding yarns L15, L16, whichtogether have the same interlacing as described above:

each binding yarn L15, L16 binds (passes over) a tern of adjacent top MDyarns 1-8 and binds (passes under) a bottom MD yarn 9-16, in particularoffset in the cross direction by an even number of machine positions(for example, four positions) with respect to the tern of bound top MDyarns.

The binding yarn L15 (FIG. 6c ) passes over (i.e. binds) the top MDyarns 1,2,3 and passes under (i.e. binds) the bottom MD yarn 15, whichis offset by four positions in cross machine direction with respect tothe top MD yarn 3; the binding yarn L16 (FIG. 6d ) passes over the topMD yarns 5,6,7 and under the bottom MD yarn 11, which is also offset byfour positions in cross machine direction with respect to the top MDyarn 7.

In all embodiments of the invention, it is possible to bind the toplayer 101 and the bottom layer 102, as well as by means of the bindingyarns extending in cross machine direction (i.e. in the weft direction)as above described, also in machine direction (i.e. in the warpdirection).

For this purpose, as shown in FIG. 7, in the fabric repeating unit 104at least a pair of overlapped MD yarns, i.e., one top MD yarn and onebottom MD yarn overlapping one another (belonging to the top layer 101and to the bottom layer 102, respectively), as for example the top MDyarn 6 and the bottom MD yarn 14 located directly under the top MD yarn14, cross each other in machine direction, i.e. in the warp direction,so as to define a pair of warp binding yarns MD6, MD14, whilemaintaining the weaving patterns of both the top layer 101 (example:four satin), and of the bottom layer 102 (example: interrupted six twillstructure).

The warp binding yarns MD6, MD14 of each pair are arranged directly oneover the other, and cross each other maintaining the same basicstructure (four satin). Each top MD yarn 1-8 and each bottom MD yarn9-16 then maintains its weaving position even if acting as a warpbinding yarn between the top layer 101 and the bottom layer 102.

In the fabric repeating unit 104 the warp binding yarns MD6, MD14 crosseach other only once.

In the unit 104 several pairs of overlapped MD yarn may cross eachother, even all the pairs, to define respective pairs of warp bindingyarns: preferably, adjacent pairs of warp binding yarns cross eachother, in offset positions, in machine direction.

It is understood that the binding in machine direction (warp) applies toall the embodiments of the invention and to all the weaving patterns ofthe fabric 100 mentioned above and others, that furthermore, fall underthe invention.

According to an aspect of the invention, the fabric 100 described aboveis used in a papermaking process, in particular in the forming sectionof a papermaking machine. The process comprises the steps of:

(A) providing a papermaking fabric as described above;

(B) arranged on the top surface of the fabric an aqueous pulp ofcellulose and/or a paper material to be formed; and

(C) removing water from the pulp and/or from the paper material to beformed.

Said process is, essentially known and well understood by those skilledin the art, therefore further details in this respect are not necessary.

It remains understood that, with what has been described and illustratedherein further modifications and alternatives can be applied which donot depart from the scope of the invention as defined in the appendedclaims.

1. A triple papermaking fabric (100), having at least one fabricrepeating unit (104) that comprises: a set of warp yarns or machinedirection (MD) yarns (1-16), that extend in machine direction (MD) andsubdivide in eight top MD yarns (1-8) and eight bottom MD yarns (9-16);a set of weft yarns or cross machine direction (CMD) yarns (P6,P10,P14;MC5,MC9,MC13; L7,L8,L11,L12), that extend in cross machine direction andspecifically comprise: three top CMD yarns (P6,P10,P14), three bottomCMD yarns (MC5,MC9,MC13) and two pairs of binding yarns (L7,L8,L11,L12)comprising respective support portions (115) and respective bindingportions (116); wherein: the top CMD yarns (P6,P10,P14) are interwovenonly with the top MD yarns (1-8) to form a top fabric layer (101); thebottom CMD yarns (MC5,MC9,MC13) are interwoven only with the bottom MDyarns (9-16) to form a bottom fabric layer (102); the binding yarns(L7,L8,L11,L12) are interwoven with both the top MD yarns (1-8) and thebottom MD yarns (9-16) so as to bind the top layer (101) with the bottomlayer (102); the binding yarns (L7,L8,L11,L12) are arranged in pairsbetween pairs of adjacent top CMD yarns (P6,P10,P14); and the bindingyarns (L7,L8,L11,L12) of each pair intersect with each other underrespective transition yarns (T), which pass over both the binding yarnsof the pair; the fabric being characterized in that: the binding yarns(L7,L8; L11,L12) of each pair, together, leave exposed on a top surfaceof the fabric (100) only single isolated transition yarns (T), allseparated from each other in cross machine direction by a plurality ofadjacent top MD yarns (1-8); and the transition yarns (T) defined by afirst pair of binding yarns (L7,L8) are offset by one top MD yarn withrespect to the transition yarns (T) defined by a second pair of bindingyarns (L11,L12).
 2. The fabric according to claim 1, wherein thetransition yarns (T) of each pair of binding yarns (L7,L8,L11,L12) areseparated from each other by terns of adjacent top MD yarns (1-8). 3.The fabric according to claim 1 or 2, wherein the sequence of the twobinding yarns (L7,L8; L11,L12) of each pair, together, with respect tothe top MD yarns (1-8) is the same as the sequence of the top CMD yarns(P6,P10,P14) with respect to the top MD yarns (1-8).
 4. The fabricaccording to claim 1, wherein the two binding yarns (L7,L8; L11,L12) ofeach pair, together, pass over three adjacent top MD yarns (1-8) andunder the following top MD yarn, and so on.
 5. The fabric according toclaim 1, wherein each binding yarn (L7,L8,L11,L12) passes over threeadjacent top MD yarns (1-8) and under the following five adjacent top MDyarns (1-8), and so on; and under one bottom MD yarn (9-16) and over allthe following bottom MD yarns (9-16), and so on.
 6. The fabric accordingto claim 1, wherein the pairs of binding yarns (L7,L8; L11,L12) areoffset with respect to the adjacent top CMD yarns (P6,P10,P14) so, as topass over the top MD yarns (1-8) which are instead left exposed by theadjacent top CMD yarns (P6,P10,P14).
 7. The fabric according to claim 1,wherein each binding yarn (L7,L8,L11,L12) binds, i.e. passes over, atern of adjacent top MD yarns (1-8) and binds, i.e. passes under, onebottom MD yarn (9-16) which is offset in cross machine direction by aneven number of positions with respect to said tern of top MD yarns. 8.The fabric according to claim 7, wherein each binding yarn(L7,L8,L11,L12) binds a tern of adjacent top MD yarns (1-8) and onebottom MD yarn (9-16) which is offset by two or four positions in crossmachine direction with respect to the third and last top MD yarn of thetern.
 9. The fabric according to claim 1, wherein each top CMD yarn(P6,P10,P14) passes over three adjacent top MD yarns (1-8) and under thenext top MD yarn (1-8), and so on.
 10. The fabric according to claim 9,wherein the top CMD yarns (P6,P10,P14) are offset in cross machinedirection by one or two top MD yarns (1-8).
 11. The fabric according toclaim 9, wherein the fabric repeating unit (104) there is a first, asecond and a third top CMD yarns (P6,P10,P14); the second top CMD yarn(P10) being offset by one top MD yarn with respect to the precedingfirst top CMD yarn (P6) and the third top CMD yarn (P14) being offset bytwo top MD yarns with respect to the preceding second top CMD yarn(P10).
 12. The fabric according to claim 1, wherein the binding yarns(L7,L8,L11,L12) and the top CMD yarns (P6,P10,P14) form a four harnesssatin structure with the top MD yarns (1-8).
 13. The fabric according toclaim 1, wherein the bottom CMD yarns (MC5,MC9,MC13) are interwoven withthe bottom MD yarns (9-16) with an “over-2/under-6” sequence.
 14. Thefabric according to claim 13, wherein each bottom CMD yarns(MC5,MC9,MC13) is offset by one position in cross machine direction withrespect to the preceding bottom CMD yarn.
 15. The fabric according toclaim 1, wherein the fabric (100) has a ratio between weft and warpyarns of 4:1.
 16. The fabric according to claim 1, wherein the top layer(101) and the bottom layer (102) are also bound in machine direction,i.e. in the warp direction.
 17. The fabric according to claim 16,wherein in the fabric repeating unit (104) at least a pair of directlyoverlapped MD yarns (MD6,MD14), i.e. a top MD yarn and a bottom MD yarndirectly overlapping one another, cross each other in machine direction,i.e. in the warp direction, so as to define a pair of binding warp yarns(MD6,MD14) maintaining the weaving patterns of both the top layer (101)and the bottom layer (102).
 18. Use of a fabric (100) according to claim1 in a papermaking machine for conveying a cellulose pulp and/or a papermaterial to be formed.